374 research outputs found
Pennsylvania Folklife Vol. 34, No. 3
• Johann Adam Eyer: Lost Fraktur Writer of Hamilton Square • Aunt Lydia • The Image of the Jew in South-Central Pennsylvania • Gertrude Rapp: Harmony Society Abbess • Aldes un Neieshttps://digitalcommons.ursinus.edu/pafolklifemag/1107/thumbnail.jp
Small crater populations on Vesta
The NASA Dawn mission has extensively examined the surface of asteroid Vesta,
the second most massive body in the main belt. The high quality of the gathered
data provides us with an unique opportunity to determine the surface and
internal properties of one of the most important and intriguing main belt
asteroids (MBAs). In this paper, we focus on the size frequency distributions
(SFDs) of sub-kilometer impact craters observed at high spatial resolution on
several selected young terrains on Vesta. These small crater populations offer
an excellent opportunity to determine the nature of their asteroidal precursors
(namely MBAs) at sizes that are not directly observable from ground-based
telescopes (i.e., below ~100 m diameter). Moreover, unlike many other MBA
surfaces observed by spacecraft thus far, the young terrains examined had
crater spatial densities that were far from empirical saturation. Overall, we
find that the cumulative power-law index (slope) of small crater SFDs on Vesta
is fairly consistent with predictions derived from current collisional and
dynamical models down to a projectile size of ~10 m diameter (Bottke et al.,
2005a,b). The shape of the impactor SFD for small projectile sizes does not
appear to have changed over the last several billions of years, and an argument
can be made that the absolute number of small MBAs has remained roughly
constant (within a factor of 2) over the same time period. The apparent steady
state nature of the main belt population potentially provides us with a set of
intriguing constraints that can be used to glean insights into the physical
evolution of individual MBAs as well as the main belt as an ensemble.Comment: Accepted by PSS, to appear on Vesta cratering special issu
Potential of Probing the Lunar Regolith using Rover-Mounted Ground Penetrating Radar: Moses Lake Dune Field Analog Study
Probing radars have been widely recognized by the science community to be an efficient tool to explore lunar subsurface providing a unique capability to address several scientific and operational issues. A wideband (200 to 1200 MHz) Ground Penetrating Radar (GPR) mounted on a surface rover can provide high vertical resolution and probing depth from few tens of centimeters to few tens of meters depending on the sounding frequency and the ground conductivity. This in term can provide a better understand regolith thickness, elemental iron concentration (including ilmenite), volatile presence, structural anomalies and fracturing. All those objectives are of important significance for understanding the local geology and potential sustainable resources for future landing sites in particular exploring the thickness, structural heterogeneity and potential volatiles presence in the lunar regolith. While the operation and data collection of GPR is a straightforward case for most terrestrial surveys, it is a challenging task for remote planetary study especially on robotic platforms due to the complexity of remote operation in rough terrains and the data collection constrains imposed by the mechanical motion of the rover and limitation in data transfer. Nevertheless, Rover mounted GPR can be of great support to perform systematic subsurface surveys for a given landing site as it can provide scientific and operational support in exploring subsurface resources and sample collections which can increase the efficiency of the EVA activities for potential human crews as part of the NASA Constellation Program. In this study we attempt to explore the operational challenges and their impact on the EVA scientific return for operating a rover mounted GPR in support of potential human activity on the moon. In this first field study, we mainly focused on the ability of GPR to support subsurface sample collection and explore shallow subsurface volatiles
Genetic variation at CHRNA5-CHRNA3-CHRNB4 interacts with smoking status to influence body mass index
Cigarette smoking is associated with lower body mass index (BMI), and a commonly cited reason for unwillingness to quit smoking is a concern about weight gain. Common variation in the CHRNA5-CHRNA3-CHRNB4 gene region (chromosome 15q25) is robustly associated with smoking quantity in smokers, but its association with BMI is unknown. We hypothesized that genotype would accurately reflect smoking exposure and that, if smoking were causally related to weight, it would be associated with BMI in smokers, but not in never smokers
Visual ecology of aphids – a critical review on the role of colours in host finding
We review the rich literature on behavioural responses of aphids (Hemiptera: Aphididae) to stimuli of different colours. Only in one species there are adequate physiological data on spectral sensitivity to explain behaviour crisply in mechanistic terms.
Because of the great interest in aphid responses to coloured targets from an evolutionary, ecological and applied perspective, there is a substantial need to expand these studies to more species of aphids, and to quantify spectral properties of stimuli rigorously. We show that aphid responses to colours, at least for some species, are likely based on a specific colour opponency mechanism, with positive input from the green domain of the spectrum and negative input from the blue and/or UV region.
We further demonstrate that the usual yellow preference of aphids encountered in field experiments is not a true colour preference but involves additional brightness effects. We discuss the implications for agriculture and sensory ecology, with special respect to the recent debate on autumn leaf colouration. We illustrate that recent evolutionary theories concerning aphid–tree interactions imply far-reaching assumptions on aphid responses to colours
that are not likely to hold. Finally we also discuss the
implications for developing and optimising strategies
of aphid control and monitoring
Science Operations for the 2008 NASA Lunar Analog Field Test at Black Point Lava Flow, Arizona
Surface science operations on the Moon will require merging lessons from Apollo with new operation concepts that exploit the Constellation Lunar Architecture. Prototypes of lunar vehicles and robots are already under development and will change the way we conduct science operations compared to Apollo. To prepare for future surface operations on the Moon, NASA, along with several supporting agencies and institutions, conducted a high-fidelity lunar mission simulation with prototypes of the small pressurized rover (SPR) and unpressurized rover (UPR) (Fig. 1) at Black Point lava flow (Fig. 2), 40 km north of Flagstaff, Arizona from Oct. 19-31, 2008. This field test was primarily intended to evaluate and compare the surface mobility afforded by unpressurized and pressurized rovers, the latter critically depending on the innovative suit-port concept for efficient egress and ingress. The UPR vehicle transports two astronauts who remain in their EVA suits at all times, whereas the SPR concept enables astronauts to remain in a pressurized shirt-sleeve environment during long translations and while making contextual observations and enables rapid (less than or equal to 10 minutes) transfer to and from the surface via suit-ports. A team of field geologists provided realistic science scenarios for the simulations and served as crew members, field observers, and operators of a science backroom. Here, we present a description of the science team s operations and lessons learned
Associations between APOE Variants and Metabolic Traits and the Impact of Psychological Stress
In a previous study, we observed that associations between APOE rs439401 and metabolic traits were moderated by chronic stress. Thus, in a population of stressed and non-stressed Danish men, we examined whether associations between APOE rs439401 and a panel of metabolic quantitative traits, all metabolic traits which may lead to T2D and CVD were moderated by psychological stress.Obese young men (n = 475, BMI ≥ 31.0 kg/m(2)) and a randomly selected control group (n = 709) identified from a population of 141,800 men were re-examined in two surveys (S-46: mean age 46, S-49: mean age 49 years) where anthropometric and biochemical measures were available. Psychological stress factors were assessed by a self-administered 7-item questionnaire. Each item had the possible response categories "yes" and "no" and assessed familial problems and conflicts. Summing positive responses constituted a stress item score, which was then dichotomized into stressed and non-stressed. Logistic regression analysis, applying a recessive genetic model, was used to assess odds ratios (OR) of the associations between APOE rs439401 genotypes and adverse levels of metabolic traits.The APOE rs439401 TT-genotype associated positively with BMI (OR = 1.09 [1.01; 1.17]), waist circumference (OR = 1.09 [1.02; 1.17]) in stressed men at S-46. Positive associations were observed for fasting plasma glucose (OR = 1.42 [1.07; 1.87]), serum triglycerides (OR = 1.41 [1.05; 1.91]) and with fasting plasma insulin (OR = 1.48 [1.05; 2.08]) in stressed men at S-49. Rs439401 TT-genotype also associated positively with surrogate measures of insulin resistance (HOMA-IR; OR = 1.21 [1.03; 1.41]) and inversely with insulin sensitivity (Stumvoll index; OR = 0.90 [0.82; 0.99], BIGTT-S(I); OR = 0.60 [0.43; 0.85]) in stressed men. No significant associations were observed in non-stressed men, albeit the estimates showed similar but weaker trends as in stressed men.The present results suggest that the APOE rs439401 TT-genotype is associated with an adverse metabolic profile in a population of psychologically stressed Danish men
Asteroids Were Born Big
How big were the first planetesimals? We attempt to answer this question by
conducting coagulation simulations in which the planetesimals grow by mutual
collisions and form larger bodies and planetary embryos. The size frequency
distribution (SFD) of the initial planetesimals is considered a free parameter
in these simulations, and we search for the one that produces at the end
objects with a SFD that is consistent with asteroid belt constraints. We find
that, if the initial planetesimals were small (e.g. km-sized), the final SFD
fails to fulfill these constraints. In particular, reproducing the bump
observed at diameter D~100km in the current SFD of the asteroids requires that
the minimal size of the initial planetesimals was also ~100km. This supports
the idea that planetesimals formed big, namely that the size of solids in the
proto-planetary disk ``jumped'' from sub-meter scale to multi-kilometer scale,
without passing through intermediate values. Moreover, we find evidence that
the initial planetesimals had to have sizes ranging from 100 to several 100km,
probably even 1,000km, and that their SFD had to have a slope over this
interval that was similar to the one characterizing the current asteroids in
the same size-range. This result sets a new constraint on planetesimal
formation models and opens new perspectives for the investigation of the
collisional evolution in the asteroid and Kuiper belts as well as of the
accretion of the cores of the giant planets.Comment: Icarus (2009) in pres
Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets
Nature, 435, pp. 466-469, http://dx.doi.org./10.1038/nature03676International audienc
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